CVE-2026-16240VulnerabilityPublished 12 Nov 2026

PostgreSQL pg_basebackup · Use of Externally-controlled Format String

Source GCVE Database

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Authoritative record:CVE-2026-16240· Low 3.7

Not known to be exploited · CVSS 3.7 Low · fixed in 18.7 : update PostgreSQL when convenient.

Data as of 12 Nov 2026, 16:20 UTC

CVSS 3.1 base score

3.7Low

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (PostgreSQL)	CVSS 3.1	3.7

Patch: Available – fixed in 18.7, 17.12, 16.16 +2

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Attack Vector: Network
Attack Complexity: High
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 12 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 12 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-qrq9-3fx6-36f2

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
PostgreSQL	Affected >=18 <18.7	Fixed in 18.7
PostgreSQL	Affected >=17 <17.12	Fixed in 17.12
PostgreSQL	Affected >=16 <16.16	Fixed in 16.16
PostgreSQL	Affected >=15 <15.20	Fixed in 15.20
PostgreSQL	Affected <14.25	Fixed in 14.25
Postgresqlpostgresql/postgresql`pkg:deb/postgresql/postgresql`Other threats	Affected <14.25	Fixed in 14.25

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade PostgreSQL to version 18.7, 17.12, 16.16, 15.20, or 14.25 or later, where this vulnerability is fixed. No other mitigation or workaround is indicated. Patch status is confirmed by the fixed versions listed.

Description

A format string vulnerability exists in PostgreSQL's pg_basebackup utility that allows an attacker with prior server compromise to potentially disclose memory contents from the backup manifest. The vulnerability does not leak data directly to the attacker, requiring additional secrets to exploit. Integrity impact is unlikely as the formatter does not support %n. Versions before PostgreSQL 18.7, 17.12, 16.16, 15.20, and 14.25 are affected.

Impact

The vulnerability allows limited disclosure of memory contents from pg_basebackup manifest bytes to an attacker who has already compromised the server. There is no impact on data integrity or availability. Exploitation requires additional implementation-specific secrets since the improperly-read bytes are not returned to the attacker’s server. The CVSS score is 3.7 (low severity), reflecting the limited confidentiality impact and high attack complexity.

CWE-134Use of Externally-Controlled Format String (opens in a new tab)
Base weaknessLikelihood of exploit: High
The product uses a function that accepts a format string as an argument, but the format string originates from an external source.
Requirements
Choose a language that is not subject to this flaw.
Implementation
Ensure that all format string functions are passed a static string which cannot be controlled by the user, and that the proper number of arguments are always sent to that function as well. If at all possible, use functions that do not support the %n operator in format strings.
Build and Compilation
Run compilers and linkers with high warning levels, since they may detect incorrect usage.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V5.4.2 (opens in a new tab)
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
Attack patterns
Format String Injection (opens in a new tab)
String Format Overflow in syslog() (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 12 Nov 2026, 16:20 UTC

WeaknessesCWE-134

Technical details

References

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